A field bus is a communication system which connects multiple field devices, such as sensors and/or actuators, to one or more control units, which are used in motor vehicle technology, for example. The field bus technology was developed in the 1980s to replace parallel wiring of binary signals or analog signal transmission typical up to that point with digital transmission technology.
In a network, topology refers to the structure of the connections of multiple devices to one another to ensure mutual data exchange. In networking in a ring topology, each two users are connected to one another via two-point connections, so that a closed ring results. The information to be transmitted is relayed from user to user, until it has reached its intended location. Methods of addressing are required to ensure the communication.
In today's field bus systems, communication nodes are situated in a linear topology (frequently referred to as a bus) or in a star topology. For communication in these topologies, it is necessary that the communication nodes either have a unique identification in the form of a name or number or the messages carry a name or a number. In the second case, the communication nodes which wish to receive a specific message must know the name or the number of the message.
One conventional computer networking technology is token ring. In a token ring, the communication nodes are logically situated in a ring. Each node has an individual identification. A special node initiates the communication in the ring in that it relays a free token to its connected node. If the next node wishes to transmit something to another node, this node first appends the node number [of the node] to which it wishes to transmit, and subsequently its useful data. It now sets the token to the state “busy.” It transmits the entire packet of the busy token, addresses, from where and to where, and the useful data one station further in the ring. The packet is relayed in the ring until the station having the correct node number receives the packet. This station receives the message and resets the token to “free.” The token is relayed to the next station in the ring.
In current field bus systems, it is disadvantageously absolutely necessary for the communication nodes either to have a unique identification or for the nodes to know the identification of the messages which are of interest to the affected nodes. In novel mechatronic systems, the electronics are frequently distributed to the mechanical components. The distributed electronics exchange information with one another via a communication system (LIN, CAN, I2C . . . ). These distributed systems are to be producible as cost-effectively as possible. One possibility for this purpose is that the distributed electronics are identical parts which do not differ by differing identification. This is impossible to implement using the current communication systems.
German Patent Application No. DE 101 38 121 A1 describes an electronic system having a first bus system based on static addresses and a second bus system having addresses given dynamically during an initialization.
European Patent Application No. EP 1 659 467 A1 describes a method for operating a network having a ring topology, a faulty connection between two users of the network being recognized by monitoring a carrier signal.